1. Field of the Invention
The present invention relates generally to heat sources and heat withdrawing sources, and more particularly to heat sources and heat withdrawing sources capable of being heated by microwave energy.
2. Description of the Prior Art
Frequently, there is a need to provide localized heat to some object, and it is often inconvenient to move the object close to an immobilized heat source such as a heat vent in a building's heating system. Many attempts have been made to provide a heat source that can readily be moved to the object to be heated. Likewise, there is frequently a need to withdraw heat from an object, and the same problems develop as with heat sources. Similar efforts have been made to rectify these problems encountered in heat withdrawing apparatuses. The typical results of all these efforts are temperature buffering substances that are contained in portable hot packs, cold packs, or hot-and-cold packs. Usually, such a substance is comprised by various component substances, some of which are best suited for giving off heat, whereas others are best suited for absorbing heat, or providing some other desirable characteristics. All of these previous substances fail in one way or another to provide an inexpensive, convenient, readily manufactured solution to the need for a portable heat realeasing and withdrawing substance. Moreover, prior substances and containers for holding them are less than ideally suited for convenient heating in a microwave oven.
U.S. Pat. No. 1,819,807, issued on Aug. 18, 1931, to Virgil R. Baysinger, discloses a exothermic chemical reactant mixture for use in hot packs. The mixture gives off heat when water is applied. The invention is largely comprised by cast iron, a relatively dense material, and thus tends to be heavy relative to the amount of surface area covered. Such heaviness could make the invention unusable in circumstances where undue pressure on the article or body part to be heated must be avoided. Also, the mixture requires an external source of oxygen and water for heat production, and hence is unusable where these substances are unavailable. The mixture also wears out after 80 to 100 hours of use, and thus has no lasting value. Moreover, the invention is not suited for acting as a heat withdrawing source, and cannot be heated in a microwave oven.
U.S. Pat. No. 3,804,077, issued on Apr. 16, 1974, to Veron L. Williams, discloses a hot pack containing an exothermic, gel-forming reactant mixture, and a cold pack containing an endothermic, gel-forming reactant mixture. These packs have a life span limited by the duration of the chemical reaction that produces or absorbs heat. Once used, they cannot practically be re-used. Also, the packs are not suitable for heating by microwave energy.
U.S. Pat. No. 3,913,559, issued on Oct. 21, 1975, to Walter B. Dandiker, shows a constant temperature device that remains at its heat of fusion temperature while it either gives off or absorbs heat. Such a device is not necessarily capable of giving off or absorbing heat subsequent to freezing or melting, respectively, especially when capable of rapid heating or cooling, as the patent discloses. Additionally, such a device is only functional as described when its heat of fusion is the temperature desired by the user. Thus, the device is not adaptable to a variety of applications. The patent lists a variety of substances, none of which is part of the applicant's invention; and none of the substances used in the applicant's invention, other than acid, is disclosed in the Dandiker patent. Moreover, there is no indication in the patent that the patented invention can or should be heated in a microwave oven.
U.S. Pat. No. 4,596,250, issued on Jun. 24, 1986, to Arthur A. Beisang, III, et al., discloses a hot-and-cold pack that retains its temperature and moldability for an extended period of time. It is intended to be capable of autoclaving, and is not designed to be heated by microwave energy. In fact, when the suggested metal-coated layer or metal particles are included, the invention would be entirely unsuitable for heating in a microwave oven. Additionally, the invention does not disclose use of a humectant, such as glycerin, polyacrylamide, mineral oil, corn starch, acid or polypropylene glycol.
U.S. Pat. No. 4,671,267, issued on Jun. 9, 1987, to Edward I. Stout, discloses a substance that retains is pliability over a wide temperature range and is intended to be heated in a microwave oven. The invention comprises a humectant, such as glycerin, entrapped in a polymer matrix, such as one comprised by acrylic acid or acrylamide monomer moieties. The invention does not disclose the use of paraffin wax, mineral oil, corn starch, or polypropylene glycol.
U.S. Pat. No. 4,756,311, issued on Jul. 12, 1988, to Sam E. Francis, Jr., shows a microwavable hot-and-cold pack including an aqueous gel. This gel does not include glycerin, polyacrylamide, paraffin wax, mineral oil, acid or corn starch.
U.S. Pat. No. 5,150,707, issued on Sep. 29, 1992, to Leslie B. Anderson, shows a hot-and-cold pack including a microwavable gel. The gel is comprised by an acrylic resin that absorbs many times its dry weight. The resin is in particulate form and bound to a substrate until water is applied. Because of the necessity for user-application of water, use of the device is limited to locations where water is readily available. Moreover, there is no teaching on the patent for the use of glycerin or other humectant, a polymer, paraffin wax, mineral oil, acid or corn starch.
German Patent 4,204,528, issued on Sep. 24, 1992, to Klaus Peter Kayser, discloses a paraffin-filled bag for use as a hot pack. There is no teaching in the patent for the use of glycerin or other humectant, polyacrylamide, mineral oil, acid or corn starch.
Japanese Patent 61-276556, issued on Dec. 6, 1986, to Jiryokusenko Nippon, discloses a low cost stomach warmer comprised by alumina and silica. Because of this composition, it would be unsuitable for heating in a microwave oven.
None of the above prior art references discloses the use of transverse ribs in a hot pack container for limiting puffing during heating in a microwave oven and for maintaining integrity of the container.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.